In signal processing, Direction of Arrival (DOA) denotes the direction from which a wave (usually a propagating wave) arrives at a point, where a set of sensors may be located. This set of sensors form what is called a sensor array. DOA estimation methods may rely on a sensor array, and many methods exist with variations in complexity and estimation accuracy.
One type of relatively simple method is based on beamforming. Beamforming may help in estimating the signal from a given direction. In such a method, a steerable beam is formed towards the angle of interest by applying a complex set of weights to each array element. The DOA of the signal can be discovered by steering the beam through all possible angles of interest, and the angle that has the maximum energy output is considered to be the DOA of the signal.
The accuracy of these methods depends on the width of the beam, which is determined by factors such as the number of array elements and the physical size of the entire array. Narrower beam width can be achieved by increasing array elements and/or enlarging the array size. Additionally, the beam width is inversely proportional to the working frequency of the array, i.e., at lower frequencies the beam width is wider and hence poorer estimation accuracy. Such inconsistent performance over frequencies becomes a problem when the signal of interest is broadband.